"Gadgie" is a colloquial term used mainly in Scotland and Northern England to refer to a man. It can be difficult to find perfectly interchangeable synonyms for this word, as it is very region-specific. Some common alternatives might be "guy," "chappy," "bloke," "fella," or "dude." In a more formal context, "gentleman" or "man" may be used instead. There are also some regional variations, such as "lad" in Yorkshire or "mate" in Australia and New Zealand. Ultimately, the choice of synonym will depend on the context, audience, and regional dialect of the speaker.